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Wintry Jan 27-28 Snow Potential Official Thread

SD said:
If I lived along hwy 158 from reidsville to @metwannabe I would be pooping in excitement this morning
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Cautiously optimistic but there are several hurdles to overcome for this to be significant (2" plus) event. If it was turning up the coast sure, but it's heading due east and exiting stage right quick, as @Poimen stated a couple of times there is really a small window of snowfall. Couple that with very wet soils, rain transitioning to snow and usually CAA slower to get here then modeled, I have tempered expectations. Although I do feel like there will be an hour or two of moderate to heavy rates which will be fun
 
BOOM!
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Welcome to the party, NAM. Interesting for the Triad crowd, the NAM sounding for 10 pm is giving a best guess "snow." It's close for sure. *IF* we can get snow by 10-11 that could make a difference.

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Good to see the NAM cave. Basically lines up with the GFS and HRRR now. I would say pay attention to its thermals and see if it sniffs out any screw job warm noses. It’s good at that.

Looks to me that the heaviest snow may be setting up from Greensboro to Durham based on the 12z short range modeling, though I should probably adjust that northward in reality.
 
Which model is better on the temps? NAM, HRRR, or RAP? Because there's a pretty good difference on them . At least for my area
 
Loganelliott99 said:
I know the 3km NAM was really good with thermals yesterday. I know this is a different set up though
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In general regardless of setup the NAMs usually (not always but usually) do a better job with thermals, if they start hinting at a warm nose it's a warning shot to pay attention
 
metwannabe said:
In general regardless of setup the NAMs usually (not always but usually) do a better job with thermals, if they start hinting at a warm nose it's a warning shot to pay attention
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Yeah I just feel like there's been a couple times this year where each model has done better than the other. Regardless, every model looks really good for your area! Good luck!
 
snowlover91 said:
Typically 3km NAM is best on thermals in my experience from past storms.
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Agree: You have to watch em all and when one is polar opposite of the rest of the bunch like the Nam was on qpf. You watch and see if the bunch trend toward it or if it trends toward the bunch.

Same deal with Sunday. The Globals all have a good size storm here except gFS currently. so watch H5 and see who iis trending toward who. Thats usually the way the pendellum will swing.

Poimen & Metwannabe: Look and maybe their is a brief window for a pivot. That would be after all of us transition to snow, cause it want happen until the Low is exiting the coast. Models dont catch those sometimes and they add a couple hours of killer rates to the equation for wherever the deform band is set up when it happens. I havent seen it on any of the loops . The cams would catch it 1st and closer in to game time this evening.
 
metwannabe said:
Being on the northern side means rates aren't as intense but that's a beautiful sounding, not even close to a warm nose

View attachment 68424
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TBH soundings look pretty similar in the Wake county area too. Temps aloft may not really be our problem, except indirectly in how they imply a shallower above-freezing layer at the surface, so changeover will be rate-driven. Here's Raleigh just before and a bit after the changeover:
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Not much of a warm nose really, in fact it looks like there's column-deep CAA, which means more of a barrier for getting lift. I wonder how much that factors into the NAM's drier forecasts. The 12z HRRR looks similar though:
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RVD said:
TBH soundings look pretty similar in the Wake county area too. Temps aloft may not really be our problem, except indirectly in how they imply a shallower above-freezing layer at the surface, so changeover will be rate-driven. Here's Raleigh just before and a bit after the changeover:
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Not much of a warm nose really, in fact it looks like there's column-deep CAA, which means more of a barrier for getting lift. I wonder how much that factors into the NAM's drier forecasts. The 12z HRRR looks similar though:
View attachment 68429
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That’s a nice sounding. You think we could get better than normal ratios with that, too, or will it be limited by the near-freezing BL temps?
 
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superjames1992 said:
That’s a nice sounding. You think we could get better than normal ratios with that, too, or will it be limited by the near-freezing BL temps?
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Yeah that's a good question. I'm not sure exactly about the details of what determines snow:liquid ratios, but I'd think having a colder profile like that means better ratios, though surface temps above freezing will quickly eat into that. I think all of that should be reflected in the Kuchera Ratios, which are not spectacular. This reminds me of the surface temp problems we had with that Feb storm last year, though I think it is to our advantage that this is occurring entirely overnight.
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Here’s what I’m going with, I’m not really sure if I should have maybe expanded this further south given the column crash but here we go, may update this later it depends (above the dashed line is a dusting to 1 inch)
(Btw @Webberweather53 i used the pixlr app (the one I use for lightning stacking) and man it’s great for making maps, thanks for the idea !) BAA4EB3F-9EC8-48A2-A6A5-669B49DF40E5.jpeg
 
This is workable NAM finally getting on the storm train.....now just need for some real banding to set up and the storm to trend slower or stronger......seems like all we have managed the last several years are these fast 3-5 hr snow events.....if this thing would just hang out for another 4- 6 hrs this would be a big win for most of NC....

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Ollie Williams said:
I have a feeling this is overdone, but I would love to be under this 50dbz band! Certainly would aid in accumulation!
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RDU gets it later in the night.
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A lot of that of course is gonna be melting layer bright band but still next to the rain-snow line, you'll have weakening warm advection coupled w/ strengthening low-level cold advection + latent heating effects aiding in a laterally propagating band of frontogenesis near the rain-snow line. My personal favorite precip type is when you're getting very wet snow/ pillows falling out of the sky and you're barely inside the rain-snow line. Accumulation efficiency is obviously not as great but it's awesome to look at.
 
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